Negative reaction - under the ancient penalty - Under the Ancient Penalty - Negative Reaction | Songs.


Use the value of G o obtained in Practice Problem 7 to calculate the equilibrium constant for the following reaction at 25C:

To see how D G values can be used to predict how reactions will go, consider the four cases you encountered in the Entropy Module : 1. D H < 0, D S > 0: This is an exothermic reaction with an increase in entropy. Thus D S univ > 0 and D G < 0. The Second Law of Thermodynamics says that such a reaction is product-favored, so a D G less than zero also means a product-favored reaction. Example:     2CH 4 (g) + 3O 2 (g) 2CO 2 (g) + 2H 2 O(g) 2. D H > 0, D S < 0 This is an endothermic reaction with a decrease in entropy. Thus D S univ < 0 and D G > 0. The Second Law of Thermodynamics says that such a reaction is reactant-favored, so a D G greater than zero also means a reaction is reactant-favored. Example:     6CO 2 (g) + 6H 2 O(g) C 6 H 12 O 6 (s) + 6O 2 (g) The minus sign in the definition of D G was given so that a negative values of D G corresponded to a product-favored process and a positive value to a reactant-favored process. Thus, a product-favored reaction will go on its own, without outside intervention, and can often be made to do useful work in the process. Thus, it is like an exothermic reaction with a negative value of D E or D H. A reaction with a negative D G is called exergonic to emphasize this. Conversely, a reaction with a positive value of D G is reactant-favored and requires the input of energy to go. Such a reaction is called endergonic . 3. D H > 0, D S > 0 This is an endothermic reaction with a positive entropy change. This sort of reaction is reactant-favored at low temperatures and product-favored at high temperatures. D G predicts the same thing, since at low temperatures the D H term of D H - T D S will dominate and D G will be greater than zero. Conversely, at high temperatures, the T D S term will dominate and D G will be less than zero. Example:     CaCO 3 (s) CaO(s) + CO 2 (g) 4. D H < 0, D S < 0 This is an exothermic reaction with a negative entropy change. This sort of reaction is product-favored at low temperatures and reactant-favored at high temperatures. D G predicts the same thing, since at low temperatures the D H term of D H - T D S will dominate and D G will be less than zero. Conversely, at high temperatures, the T D S term will dominate and D G will be greater than zero. Example:     N 2 (g) + 3H 2 (g) 2NH 3 (g) Select positive or negative signs for D H and D S to see what sort of reaction results. Click on the mouse icon at left to clear the radio buttons and text. Sign of D H Sign of D S Sign of D G Product-favored? Positive endothermic exothermic Positive negative
(exergonic) positive
(endergonic) T-dependent T-dependent yes no yes at low T, no at high T no at low T, yes at high T Negative Negative D G and Reactions

Elementary (single-step) reactions do have reaction orders equal to the stoichiometric coefficients for each reactant. The overall reaction order, . the sum of stoichiometric coefficients of reactants, is always equal to the molecularity of the elementary reaction. Complex (multi-step) reactions may or may not have reaction orders equal to their stoichiometric coefficients.


Negative Reaction - Under The Ancient PenaltyNegative Reaction - Under The Ancient PenaltyNegative Reaction - Under The Ancient PenaltyNegative Reaction - Under The Ancient Penalty

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